A front car of a high speed railcar has a three-dimensional streamline shape and is formed such that an outside plate of a front car bodyshell is machined to have a predetermined curved shape. The outside plate of the front car bodyshell may be manufactured by bending a metal plate by manual work or the like or may be manufactured by cutting a metal material by machining. In the case of manufacturing the outside plate by the bending, the outside plate has a three-dimensional curved surface, so that the outside plate does not have a flat surface serving as a reference. Therefore, mounting dimension control is difficult when performing work of fixing the outside plate to a frame of the car. In contrast, in the case of manufacturing the outside plate by the machining, the metal material needs to have a machining reference surface used to fix the metal material to a surface plate of a machining device. However, since the outside plate has the three-dimensional curved surface, the machining reference surface does not normally coincide with a mounting reference surface necessary when mounting the outside plate to the frame of the car, so that the machining reference surface cannot be utilized as the mounting reference surface.
According to a method of manufacturing a curved plate in PTL 1, point marks are formed at predetermined positions of an outer peripheral portion of the press-formed curved plate. The point marks are placed on jacks of the machining device, and the heights of the jacks are adjusted to reference heights. Ribs are formed by cutting one of surfaces of the curved plate by the machining. By further cutting the other surface of the curved plate, the curved plate is finished to have a predetermined shape and a predetermined thickness. Finally, the outer peripheral portion of the curved plate is trimmed.